Printing telegraph system



Jan. 21,1936. 7 T. CORWIN PRINTING TELEGRAPH SYSTEM Filed July 14, 193 2 Sheets-Sheet l Quit uum I NI/ENTOR T. L. CORW/N ATTORNEK Jan. 21, 1936. T. L. coRwlN PRINTING TELEGRAPH SYSTEM Filed July 14, 1934 j 2 Sheets$heet 2 INVENTOP T. L.CORW/N AATTORNEY Patented Jan. 21, 1936 ITED STATES PRINTING TELEGRAPH SYSTEM Thomas L. Corwin, Newark, N. J., assignor to Bell Telephone Labcratories,. Incorporated,

New

York, Y., a corporation of New York Application July 14, 1934, Serial No. 735,172

1 Claim.

This invention relatesto-improvements in tele-.

In furnishing teletypewriter exchange service over telegraph lines to attended or unattended subscribers printing telegraph stations, it is necessary to switch a subscribers ringer out of the subscribers telegraph line whenever that subscribers teletypewriter is switched into the line for communication with. an operator at. a central printer ofiice or at another subscribers printer station. When communication has ceased between these stations, it is necessary to switch the subscribers teletypewriter out of. the line and to switch the ringer back into the line; It is desirable that the switching arrangement used for switching a subscribers ringer into and out of a telegraph line can be an automatic arrangement in order that it may be used at either an attended or an unattended teletypewriter station. a

When such a switching arrangement is used, it is advisable to employ a signaling arrangementfor notifying the operator at a calling tele-;

typewriter station that the ringer has been switched out of the line and that the teletypewriter has been switched into the line and is ready for communication. It is important that such a signaling arrangement-should not give a signal to a calling operator untilthe motor of the teletypewriter at the called printer sta-;

unattended stations.

an improved arrangement for controlling the operation of a teletypewriter motor located at a distant printer station.

Still another object of this invention is to provide an improved signaling arrangement for notifying the operator at a calling printing telegraph station that the motor of the teletypewriter at a. called printing telegraph station has started and has actually attained its full operating speed.

These objects are accomplished chiefly through the use of a centrifugal contact device which is connected to the shaft of the motor of the teletypewriter which is to be switched into the telegraph line. Since the centrifugal contact device does not operate until the motor has started and has come up to the proper operating speed, there is no danger of the printing of false characters due to the teletypewriter being operated prematurely. f l

In the case of an attended teletypewriter sta-' tion, the attendant originates a call by momentarily pressing a key. The operation of this key closes a path which enables current from a local power supply at that station to energize a relay. When this; relay becomes energized, it operates its armature thereby closing a path from the local power supply to the teletypewriter motor and, at the same time, closing a locking-up circuit for this relay. Current from the local power supply is now able to cause the operation of the teletypewriter motor and also the rectifier or motor-generator set associated with it.

When the teletypewriter motor has come up to its proper operating speed, it causes the centrifugal contact device (which is connected to the shaft of the motor) to operate a switch which removes the subscribers ringer from the line and switches the teletypewriter'into the line.

After communication has ceased, the operator at either station may send a disconnect signal which opens the locking-up circuit for the relay at the subscribers station. When this lockingup circuit is opened, the relay becomes non-0p erated and releases its armature. This opens the circuit from the local power supply through the teletypewriter motor with the result that the motor stops. The stopping of the motor causes the centrifugal contact device to return to its former condition thereby disconnecting the tele typewriter from the line and connecting the ringer back into the line.

If an operator at a central teletypewriter ofiice. wishes to call a subscriber, the operator applies. ringing current to the line thereby operating the subscribers ringer. If the subscriber is present, he presses the key mentioned above which causes his motor to start in the manner describedabove. If the subscriber is absent, or if it is an unattended station, the operator will receeive no answer to her ring. She will then apply negative battery to the line by means of a key at her central office. This will cause a polarized relay at the subscribers station to become energized. When this polarized relay becomes energized, it operates its armature thereby closing a path which enables current from the local power supply at that subscriber's station to energize the relay mentioned above in the same manner that the key did as described above. When this relay becomes energized, it causes the operation of the teletypewriter motor and its associated rectifier or motor-generator set as was described above. The motor is stopped by the transmission of a disconnect signal as was alsodescribed above.

The invention will now be described in detail with reference to the drawings in which:

Fig. 1 shows a preferred embodiment of the invention, in which a subscribers station A is connected to a subscribers station B through a central oflice C;

Fig. 2 shows an alternative arrangement in which subscribers station Sis connected to operators position P through concentrating position C; and

Fig. 3 indicates a practical method of construction for the centrifugal contact device used in the arrangements shown in Figs. 1 and 2.

Referring particularly to Fig. 1, a subscribers station A is shown in abbreviated fashion and connected by a telegraph line I and 2 to a jack 4I associated with plug 9 located at central oflice C. Likewise subscriber's station B is shown connected by a telegraph line I9 and 28 to a jack 43 associated with plug IB at central office C. Central ofiice C is shown as a double plug ended cord circuit arranged to connect subscribers stations A and B in telegraphic communication. In subscriber stations A and B and central ofice C only those portions of the circuit necessary to the complete understanding of the invention are shown.

It will be assumed that the subscriber at station A has initiated a call and, after plug 9 has been inserted in jack M, has transmitted to the central oflice operator the code of the desired line. The'central office operator then inserts the plug I8 of the cord circuit into the jack 43 associated with the desired subscribers line I9 and tacts of relay II, sleeve conductor of plug I6, and

then to ground on the sleeve terminal of the jack 43 associated with line I9 and. 20. The operation of ringing. key I3 connects ringing current to the ring conductor 28 and rings the subscribers bell 22 in a circuit traced from grounded alternating current generator II, lower front contact of key I3, the winding of relay I'l, ring conductor of plug I6, ring spring of the jack 43, ring conductor 20, normal contacts of key 2 I, the winding of ringer 22, condenser 23, through the normally made contacts of centrifugal contact device 25, and then to ground.

If the subscriber is present he will answer the call in the usual manner by operating key 36. If, however, the station is unattended, provision is made for starting the substation apparatus by the momentary operation of key I4 at the central ofiice. The operation of this key I4 removes positive battery II] from the tip conductor I9 and substitutes negative battery I5. This opsuch a way that the normal battery I0 is in a direction to non-operate it but when negative battery is applied to the line I9 it operates. The path for operating relay 28 is traced from grounded negative battery I5, operated contacts of key I4, tip terminal of plug I6, tip spring of jack 43, line conductor I9, the winding of receiving relay 29, the winding of polarized relay 28, break contacts 21, sending contacts 26, through the normally made contacts of centrifugal contact device 25, and then to ground.

When polarized relay 28 operates, it starts the motor 24 and connects the local source of power supply to rectifier 32 in order to make the subscribers teletypewriter apparatus ready to receive printer pulses. Thus, when relay 28 operates, it causes the operation of power relay 35 in a circuit traced from power supply conductor 33, the winding of power relay 35, the contacts of relay 28 to power supply conductor 34. When relay 35 operates, it looks up through a circuit traced from power supply conductor 34, stop bar contacts 38, emergency stop key 31, upper front contact and winding of relay 35, and then to power supply conductor 33. The operation of power relay 35 connects the power supply conductors 33 and 34 to the motor 24 and also to rectifier 32 through the lower contacts of relay 35. Rectifier 32 may be any well-known rectifying apparatus, such as a full wave copper oxide rectifier. Its function is to rectify the alternating current from the local source of alternating current power supply for operating printer magnet 3-I through resistance network 3B'and the contacts of receiving relay 2 9..

When motor 24 attainsitsfull operating speed, centrifugal contact device 25 (whose action will be described in detail later) breaks its normally closed back contact and closes its front contact. This action short-cicuits ringer 22 and condenser 23 and removes ground from tip conductor I9 connecting it instead through the receiving teletypewriter apparatus to ring conductor 20; This closes the communication circuit which leads from battery I0, normal upper contacts of key I3, normal contacts of key I4, the tip terminal of plug I6, jack 43, tip-conductor I9, the windings of receiving relay 29 and polarized relay 28, break contacts 21, sending contacts 25, front contacts of centrifugal device 25, recall contacts 2|, ring conductor 28, ring terminal of plug I6, the winding of relay Il, lower normally made contacts of key I3, lower normally made contacts of key I2, ring terminal of plug 9, jack 4|, ring conductor 2, front contacts of centrifugal device 8, sending contacts 5, break contacts 4, the winding of receiving relay 3, tip conductor I, tip terminal of plug 9, through the upper normally made contacts of key I2- and then to battery IE1. Relay I? operates in this cicuit and opens the circuit to lamp I8 thereby extinguishing it. as a signal to the operator at central ofiice C that the teletypewriter apparatus at subscribers station B is ready to receive printer pulses. V

The apparatus at station B remains in condition for receiving printer pulses with the motor 24 running until a preassigned signal (or combination of significant current variations) is sent, such as upper case H. When this preassigned signal is received, it operates certain selecting mechanism .and functionv bails of the subscribers teletypewriter so as to open the stop bar contacts 38. When stop bar contacts 38 open, they open the locking-up cicuit for relay 35 and cause it to release. The release of relay 35 opens the iii power circuit from power supply conductors 33 and 34 to motor 24 and'rectifier 32 thereby discontinuing their operation. After motor 24'has slowed, down appreciably, centrifugal contact device 25.

breaks its front contact and makes its back contact thus restoring the subscribers teletypewriter apparatus to its normal condition by removing the short circuit from ringer 22 :and condenser 23 and reconnecting them in circuit with the ring conductor 20 to ground, reconnecting the tip conductor I9 through polarized relay 28 to ground, and opening the direct current circuit between the tip conductor I9 and the ring conductor 20.

An alternative arrangement for accomplishing the same result is shown inrFig. 2 where a central office I operators position circuit P is shown connected to the subscribers teletypewriter' apparatus S through a concentration, board'C. The

subscribers station S is connected to the con-.

centration board C by line'conductor I 0| and the circuit is arranged so thatin the normal unoperated condition the line is closed to alternating current through a winding of alternating current relay I05 but is open to direct current by reason of condenser I02. Power from the local source of power supply is connected to motor I I2 by motor control relay I 04 which is energizedover the'line,

circuit after alternatingcurrent relay I05'has been operated. Motor I I2 is equipped with a centrifugal contact device II3 (which will be described later and which isshown; in detail in Fig. 3). Afterthe motor H2 has attained its full operating speed, centrifugal-contact device I I3 closes its contacts and reduces the resistance of.

relay I04 to such a degreethat its effect on the operation of receiving relay I88 is .not appreciable but the reduction in resistance is sufficient to operate relay I24 in the operator's position circuit P. When relay I24 operates it closes a circuit to operate an alarm device, such as lamp I32, as a signal to the operator that the substation apparatus is ready to receive printer pulses.

In order to initiate a call, the subscriber at station 5 operates key I I4 thereby closing a circuit to operate and lock relay I I! at the concentration board C. The operating path for relay H1 is traced from grounded battery II9, inner back contact of relay IIB, left-hand winding of relay II'I, tip spring of jack ,I I6, tip spring of jack I I5, variable resistance I20, subscribers line conductor IOI, key II4, through the winding of restoring relay I03, and then to ground. The locking circuit for relay I I1 is traced from grounded battery I I0, outer back contact for relay II8, righthand winding and inner front contact of relay I I I, and then to ground. When relay I I I operates, it closes a circuit from ground on its outer front contact through the filament of line lamp I2 I, and then to battery thereby lighting the lamp I2I as a line signal. I

The concentration board operator answers the call by inserting a plug, such as plug I22 associated with an idle operators position, in jack IIS associated with lamp. I2I. Relays H3 and I25 are then energized in a circuit traced from and I31 in series through the back contact of relay I39, and then 'to ground. Lamps I31 and I38 light in this circuit as a busy signal. The operation of relay I25 also connects alternating cur-.

rent from alternating current generator I26 superimposed on direct current from grounded battery I2! through the left-hand inner front contact of relay I25, right-hand winding and righthand back contact of relay I24, tip conductor Springs A close the subscribers line to direct current and cause the operation of motor control relay I04 in a circuit traced from grounded battery I2'I, the winding of alternating current generator I 25, left-hand inner front contact of.

relay I25, the right-hand winding and righthand back contact of relay I24, tip conductor I22, tip spring of jack II6, tip spring of jack II5, variable resistance "I20, line conductor IOI, set of springs Aassociated with armature I06, lefthand winding of relay I 04, the winding of receiving relay I08, through sending contacts I09 and then to ground. The circuit just traced includes a winding of relay I24 but this relay, being marginal, does not operate at this time.

The operation of motor control relay I04 connects the local source of power supply to motor 1 H2 through its right-hand outer front contact. The operation of relay I04 disconnects the operating path to alternating current relay I05 through its right-hand inner back contact and also disconnects the circuitfrom battery IIO to' restoring relay I03 at the left-hand back contact of relay I04. In order to prevent the false operation of restoring relay I03 after relay I05 has operated and before relay I04 has had sufficient time to operate, spring assembly A and B is so constructed that contacts A close an appreciable time before contacts B close. In this way, sufficient time is obtained for relay I04 to operate and break its left-hand'back contacts before springsB close the circuit to restoring magnet I03. The opening of the operating circuit of relay I05 does not, cause armature I06 to restore. Consequently, contacts A and B remain closed until the operation of restoring relay I03.

When motor II2 reaches its full operating speed, centrifugal contact device II3 closes its contacts and reduces the resistance of relay I04 in the line circuit by placing the right-hand winding of relay I04 and'resistance I01 in parallel with its left-hand winding. This'reduction in the line resistance is suflicient to operate marginal relay I24 over the line circuit previously described. The operation of marginal relay I24 opens the circuit from alternating current generator I25 superimposed on direct current battery I2! at the right-hand back contact of relay.

I24 and connects the line circuit through the right-hand front contact of relay I24, sending contacts I30, the winding of receiving relay I29, through the right-hand outer front contacts of relay I25, and then to battery I28.

Relay I24 locks up in a circuit traced'from battery I50, through the'left-hand contacts and winding of relay I24 through the left-hand outer frontcontacts of relay I25, and then to ground.

The leftehand' lockinguprcontact of relay I24 is" adjusted to close the circuit to the left-hand winding of relay I24 before its right-hand contacts break the circuit to theright-handv winding in order'to insure the complete operation of relay I24. Relay I24 in operating also closes a circuit from battery I50, through its left-hand front contact, through the filament of lamp I32, and then to ground thereby lighting the lamp I32 as an indication that the subscribers station S is ready to receive printer pulses.

Due to the fact that centrifugal contact device II3 does not close its contacts until motor II2 has actually reached its full operating speed, there is no danger that a signal will be given to the operator at P before the motor-is ready. This constitutes an improvement over other methods which. only operate after a mere time delay regardless of whether the motor I I2- is actually operating. The operator at'position P noting the lighting of this lamp I32, operates key I33 which connects battery I5I to the winding of relay I34 thereby operating relay I34. Relay I34 locks up from ground, through its left-hand front contact, through the left-hand front contact of relay I24, then to battery I50. Relay I34 also closes a circuit from battery I52, through its right-hand front contact, through motor I35, and then to ground thereby operating, motor I35.

The circuits and apparatus are now in a posi-' tion to send and receive printer pulses. When the communication has ended the central station operator operates key I40 which operates relay I39 in a circuit traced from'grounded battery I53, through the right front contact of relay I29, through the winding of relay I39, key I40, and then to ground. When relay I39 operates, it locks up through its own contacts and opens the circuitto the filaments of lamps I31 and I38. The central station concentration board operator noting the extinguishing of lamp I38, removes plug I22 from jack II6, thus breaking the circuits through motor control. relay I04 and relays IIRSand I25. Relay H8 is of the slow-to-release type in order that relay I04 may release first and permit the operation of restoring magnet I03 to open the line circuit to direct current before relay IIB closes itsv back contacts and reconnects relay III to the line. In this way, the false operation of relay I I1 is prevented;

Relay I04, in releasing, closes a circuit from grounded battery IIO, inductance III, left-hand. back contact of relay I04, contacts B associated with armature I06, through the winding of restoring relay I03, and then to ground. Relay I03 operates and restores armature I06 to its original osition, thereby opening contacts A and B associated with it and also opening line IOI to direct current. In releasing, relay I04 also disconnects the local power supply from motor II2 allowing it to come to rest. When motor II2 does come to rest, it causes the centrifugal con:- tact device I I3 to open its contact and to thereby restore the alternating current circuit from line conductor IOI through condenser I02 to relay I05 through theright-hand inner back contacts of relay I04. In opening its contacts, centrifugal device II3 removes the right-hand winding and resistance I0I from the parallel circuit with the 0 left-hand winding of relay I04..

At the central oflice, the release of relay I25 opens the circuit and; releases relay I24, opens thecircuit to lamps I31: and I 38 to prevent them from. rte-lighting, opensqthe circuit to receiving relay I29 (allowing it to release), and opens the circuit to relay I34 permitting this relay to release. and open the circuitto motor I35. The release of. relay I129; opens the circuit to relay I39 allowing it. to release. All circuits at both the central oftice andsubscribers station are thus restored to their normal condition as shown in Fig.2.

The operation of the system when a call is initiated at the central station is similar to that justdescribed and so need not be explained here.

Fig.3 shows the details of the centrifugal contact device used in Figs. 1 and 2. It is of the well-known fiyball. governor type in which, upon therotation of shaft 50 which is connected to the motor, the bracket 5I and arms 53 with flyballs 52 rotate with it. When the motor has reached its full operating speed: the centrifugal force (due to the rotation) forces the flyballs 52 outward and causes arms 53 to rotate on their pivots thereby pushing. operating shaft 54 in a longitudinal directionv to the left against the pressure of retractile spring 55. Themotion of shaft 54 in: a longitudinal direction to the left causes armature 56 to break the circuit with its back contact-and make the circuit with its front contact. Conversely, when the motor slows down, flyballs 52 will dropinwardly and cause arms 53 to resume the-positionshown. in Fig. 3. This will pull the operating shaft 54'- back to the right which", in turn, causesarmature 5B (biased by spring 59 to break its front contact and make its back contact.

The above arrangements have been shown in order toillustrate the principles of this invention. It is to be understood that different arrangements. employing the principles of this invention maybe designed. Accordingly," the invention is not to be limited tothe arrangements shown in the drawings, but isto be restricted only by the claim appendedhereto.

What is claimed is:

A teletypewriter system having a central teletypewriter office with a concentration board, a subscribers teletypewriter connectable to the concentration board. by only a single wire telegraph line, said line being normally closed to alternating current and normally open to direct current, a normally unoperated teletypewriter motor located; at the subscribers station, motor starting means at the subscribers station for starting .the motoncontrol means at the concentration board for applying alternating current to the line to operate the motor starting means for starting themotor, a normally unoperated instrumentality for varying the direct current resistance of the line, said instrumentality being operated only by the teletypewriter motor and only when the motor has attained its full operating speed, and a. normally unoperated indicating device at the central oflice operating in response 7 THOMAS L. CORWIN. 

